The Senate trial of President Clinton could look like anything from a tedious rehashing of the existing evidence, accompanied by dressed-up legalistic arguments, to a full O.J. Simpson-style spectacle, with Chief Justice William H. Rehnquist in the improbable role of Judge Lance Ito.

The elaborate procedure endorsed Friday by a unanimous Senate guarantees only that the toughest fights -- over whether to permit live testimony, as the House "managers" demand and the White House is seeking devoutly to avoid -- are postponed for at least a few weeks.

But with motions due Monday and opening presentations starting Thursday, the evidence that Clinton obstructed justice in his efforts to conceal his relationship with Monica S. Lewinsky and then lied under oath to the grand jury will receive its fullest airing since independent counsel Kenneth W. Starr's report hit the Internet in September.

Yesterday, as Senate Majority Leader Trent Lott (R-Miss.) vowed in a radio address to insist on "high standards of decency and decorum" in the historic trial, White House lawyers and the 13 House Republican prosecutors were considering the major strategic decisions they must make over the weekend and early this week. Clinton's defense team met through much of the day and the House prosecutors planned to meet Monday to ready a new plan for a much more extensive opening presentation than they had envisioned.

"We're going to have to go back to the drawing board and see how to proceed within that time frame," said Rep. Charles T. Canady (R-Fla.), one of the managers.

The White House must decide which pretrial motions and defenses it should raise at this stage as it seeks to strike a balance between not enraging the jury of 100 senators with overly "hairsplitting" legal arguments and not abandoning any promising lines of attack. The House team must retool a plan for an aggressive prosecution that has made key senators in both parties wary of a trial that could hinge on salacious details.

And both sides find themselves in the strange legal position of figuring out how to use their 24 hours each, likely spread over three days, to present their best case while not knowing whether any witnesses will follow or who they will be.

The issues include mundane matters -- among those being considered was whether the antiquated Senate rules allow the lawyers to wheel television monitors onto the Senate floor to present snippets of videotaped testimony -- along with fundamental questions about the case.

White House advisers, for example, were debating whether to concentrate on unraveling the case against Clinton or to use some of their time to revive attacks on Starr and his investigation. And for days the House GOP prosecutors have discussed whether they should seek to introduce evidence not weighed by the House during its impeachment proceedings last month.

White House Options

The White House will be the first side heard from this week, when on Monday it submits its answer to the Senate summons and, later in the day, any pretrial motions. (House managers have until 5 p.m. Monday to make their pretrial motions as well, but none are expected beyond perhaps some procedural matters.)

The White House can present any number of arguments in its filing Monday or trial brief due Wednesday: that the articles should be dismissed because they were passed by a lame-duck House (an argument that is likely to be muted, if it is raised at all, in part because Senate Democrats have argued that it is not a productive approach); that the articles are too vague to defend against; and that they were improperly and unfairly drafted by lumping numerous allegedly impeachable acts together in a single count.

The White House at that stage could make a preemptive bid to have the case tossed out on grounds that the allegations against Clinton, even if true, do not merit his ouster.

But because the agreement forged by the Senate contemplates hearing such a motion to dismiss at the close of the oral arguments, and because it is unlikely that a majority would vote to dispose of the case before at least taking that step, the White House may choose to refrain from making a motion to dismiss on Monday. That would allow it to avoid suffering a political setback and having senators put themselves on record this early in the trial.

On Wednesday, the House will respond to the White House argument and the Senate will hear from both sides, debate and vote on the pretrial motions.

The opening arguments beginning Thursday, first by the House and then next Tuesday by the White House, inevitably will proceed along a strange dual track: the lofty constitutional plane of the meaning of "high crimes and misdemeanors" and the nitty-gritty, often sordid, factual level of disputes over events and their implications.

With the uncertainty over the trial's procedure only resolved Friday, each side has not yet made such basic choices as who will argue and how those 24 hours will be divided, beyond White House officials suggesting that counsel Charles F.C. Ruff is likely to do most of their arguing and House GOP sources saying they are rethinking the initial plan for Rep. F. James Sensenbrenner (R-Wis.) to open their case.

Both sides agree there will be some differences from last month's clash in the House Judiciary Committee over the articles. In part, that's because the House last month rejected two of the four proposed articles of impeachment reported out of the committee, those accusing Clinton of lying in his deposition in the Paula Jones case about Lewinsky and abusing the powers of his office by submitting "perjurious, false and misleading" answers to the 81 questions propounded by the committee.

White House officials believe the defeat of the article alleging perjury in the Jones deposition helped them. Even Ruff had acknowledged during his appearance before the House Judiciary Committee that "reasonable people . . . could determine that [Clinton] crossed over that line" and gave false testimony at the deposition.

Now, the White House is relieved that, as it sees the articles, it is freed of the necessity of defending the president's deposition statements, such as his assertion that he had no specific recollection of being alone with Lewinsky.

But the House managers are not likely to abandon Clinton's deposition statements when they make their presentation. They note that Clinton testified before the grand jury that he told the truth during the Jones deposition; they say that is one of the elements of their grand jury perjury case against Clinton and therefore sweeps in all the allegedly false statements he made during the Jones deposition.

"I don't think it will affect the proof that is presented because you have to lay the same evidentiary foundation for Article I as if you had both articles in there," Rep. Asa Hutchinson (R-Ark.) said. "But I'm sure that the presidents' lawyers will argue the insignificance of the deposition since the House did not vote that as a separate article."

Motion to Dismiss

Once the oral arguments have concluded and the senators have questioned the two sides for up to 16 hours -- via written queries posed by Rehnquist -- the Senate will entertain a motion to dismiss the case. That would conclude the matter, making it the only impeachment trial since the Senate's first impeachment -- of Sen. William Blount in 1797 -- to end without hearing from witnesses.

But before a vote on dismissal, the House managers will get their shot at arguing why they need to present witnesses and, if they want, to bring in evidence that was not before the House as it voted to impeach the president and will not be allowed in Senate opening statements.

The procedure settled on by the Senate for making this decision was designed to avoid a repeat of the process that subjected the House to widespread condemnation when it unleashed the Starr report before determining that it was fit for public consumption.

Many of the 100 senators are veterans of the confirmation hearings of Supreme Court Justice Clarence Thomas seven years ago, in which the nation was treated to a riveting discussion of "Long Dong Silver" and pubic hairs on Coke cans, and they are determined not to repeat that by having Lewinsky elaborate on the Senate floor about precisely what the president touched and why he touched it.

The impeachment trial rules present a series of hurdles before such incendiary evidence ends up unedited on the Senate floor. The first is to persuade a majority to approve pretrial questioning of any prospective witnesses in the form of depositions. After any depositions are taken -- and the senators therefore have a heads-up about what is coming -- either side seeking to call a particular witness would face a second obstacle in the form of a vote to allow the witness to testify in person.

Both the White House and the House prosecutors were wary of this process. In fact, the ability of the House to make its case for witnesses before a dismissal vote -- rather than waiting to proceed to that question if the motion to dismiss is defeated -- was a major sticking point as the finishing touches were put on the agreement Friday and almost caused the discussions to collapse, congressional sources said. The final deal gives the House three hours to explain which witnesses it wants and why, immediately followed by the White House argument against.

That setup has the White House concerned that the House prosecutors, after days of repeating now-familiar evidence concerning Lewinsky, will seize the opportunity to make new allegations against the president, possibly swaying the Senate to vote against dismissal. Clinton's defenders will have to present their rebuttal without any advance notice of which witnesses the House will seek to call and without any ability to determine for itself what those witnesses have to say.

Although White House lawyers are familiar with testimony of witnesses like Vernon E. Jordan Jr. and Betty Currie, they have not seen the evidence amassed from any potential new witnesses such as former White House volunteer Kathleen E. Willey and could be expected to protest that her testimony was not considered by the House and is not relevant to the articles of impeachment.

Some Senate experts said that House managers could have a tough time persuading the Senate to allow them to depose witnesses not heard from in the House proceedings.

"They'll have to persuade the Senate and they'll have, one can predict, a difficult time if they didn't think at the time of formulating these articles that those matters were relevant," said former Senate legal counsel Michael Davidson.

The House managers, if they seek to bring in witnesses like Willey, would contend that any evidence that Clinton or his allies sought to discourage Willey from making public, such as her claim that Clinton made unwanted sexual overtures to her at the White House, is relevant to whether he made similar efforts to have Lewinsky cover up their affair.

And the managers could argue that the House refrained from considering the Willey evidence, not because it was irrelevant but because Starr asked them not to make it public as he continued his investigation, which resulted in the indictment last week of Willey's friend, Julie Hiatt Steele.

Rules of Evidence

In making decisions about what evidence to allow, the Senate is not bound by the federal rules of evidence that limit prosecutors' ability to bring in evidence of a defendant's "prior bad acts," although it could be expected to use them as a guide.

Under the Senate rules, the first crack at making such evidentiary rulings is up to Rehnquist, although he can take a pass on the issue and have the senators decide on a majority vote. The Senate can also overrule the chief justice, and indeed did so repeatedly in the first presidential impeachment trial, of Andrew Johnson in 1868. But this time around, with the entire nation watching on live television, it might be reluctant to do so for fear of looking political.

In a closed-door meeting with House Judiciary Republicans Friday afternoon, several conservative senators indicated conflicts in testimony will be "an important criteria for calling witnesses," according to Hutchinson, which would still leave the door open for testimony from Lewinsky and Currie, whose grand jury testimony conflicts on the key question of who initiated Currie's retrieval of presidential gifts to Lewinsky that were under subpoena in the Paula Jones lawsuit.

But managers are still concerned about the prospect of having to depose all witnesses before bringing them to the well of the Senate.

"If you have witnesses who have previously testified five times before the grand jury, it's a little problematic to require another deposition under oath before they take the witness stand," Hutchinson said.